Mechanical problems and thromboemboli have limited progress in the development of the artificial heart. An interdisciplinary group was established at The Pennsylvania State University in 1971 to develop a mechanically-sound, thrombus-free-artifical heart. The first heart replacement by our group was performed in December of 1973. Ten of our last 11 calves to have heart replacement have survived operation and lived 2 1/2 to 12 1/2 days. However, poor washout in the apex of the pump led to thrombus formation and emboli in most instances as the terminal event. The power unit and automatic control system have been shown to function well in bench studies and in actual heart replacement studies. An improved pump has recently been designed, "transverse tether sac pump," and employed for long term left ventricular assist. This pump has considerably improved washout and has been free of thromboemboli. We propose to perform artificial heart implantation in calves using the improved, transverse tether sac as well as evaluate other pump designs. Instrumentation is available to maintain 2 calves simultaneously each with total heart replacement. Special consideration will be given to characterization of the bulk and surface properties of segmented polyurethane prior to and after implantation to identify and eliminate factors associated with thrombus formation. Detailed hematologic studies and organ evaluation will be carried out. Further evaluation of the automatic control system will be obtained, including the use of vasoactive drugs and treadmill exercise. Complete autopsy studies will be performed. Our group is well established and represents specialists in a variety of areas necessary for such a multifaceted project. We firmly believe the artificial heart will be a useful therapeutic device in the future.